Refrigeration apparatus



Feb. 7, 1967 Filed April 7, 1964 H- J. T. SMITH REFRIGERATION APPARATUS3 Sheets-Sheet 1 Feb. 7, 1967 H. J. T. SMITH REFRIGERATION APPARATUS 3Sheets-Sheet 2 Filed April 7, 1964 Feb. 7, 1967 H. J. T. SMITH 3,302,422

REFRIGERATION APPARATUS Filed April 7, 1964 3 Sheets-Sheet :5

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I L 0-24 0285 0525 0570 TIME (SECONDS) United States Patent 3,302,422REFRIGERATlON APPARATUS Howard John Treweelr Smith, Bognor Regis,Sussex, England, assignor to Petrocarhon Developments Limited, London,England, a British company Filed Apr. 7, 1964, Eer. No. 357,202 Claimspriority, application Great Britain, Apr. 10, 1963, 14,351/ 63 18Claims. (Cl. 62-456) This invention is concerned with improvedrefrigeration appartus, and with an improved method of producingrefrigeration.

Refrigeration at low temperatures of the order of 200 K. and down tovery low temperatures of the order of K., is required in smallquantities, for an increasing number of scientific purposes, forexample, for use in connection with infrared detectors, masers andcryotrons. The usual methods of .producing refrigeration for thesepurposes are either by expansion using a piston expansion device or byexpansion through a Joule-Thomson valve. The first method has thedisadvantage that it involves parts moving at low temperatures, whilethe second method has the disadvantages that it involves very highpressures, of about 2,000 pounds per square inch and that, if it is tobe operated in more than one stage, different working gases are usuallyrequired in the several stages.

It is an object of this invention to provide refrigeration at low orvery low temperatures which includes no mechanical parts moving at lowtemperatures, which operates at relatively low pressures, e.g. pressuresnot above 300 p.s.i.g., and which can operate in stages withoutrequiring the use of different working gases in the several stages.

The present invention includes refrigeration apparatus comprising atubular member which is open at one end and closed at the other end, athermal regenerator in communication with the open end of the tubularmember, a gas conduit in communication with the thermal regenerator sothat gas under pressure may be passed from the gas conduit through thethermal regenerator to the tubular member and exhausted with expansionfrom the tubular member through the thermal regenerator to the gasconduit, the thermal regenerator serving to abstract heat from gasentering the tubular member and return heat to gas leaving the tubularmember, valve means in said gas conduit for controlling the flow of gasto and from the tubular member and arranged to permit the gas to enterand leave the tubular member as a succession of charges and heatexchange means adjacent the closed end of the tubular member forenabling a coolant to be passed in thermal contact with the tubularmember adjacent to the closed end thereof, whereby on operation of theapparatus with gas under pressure being fed into, and exhausted withexpansion from, the tubular member as a succession of charges and with acoolant passing through the said heat exchange means refrigeration ismade available near the open end of the tubular member adjacent thethermal regenerator.

The present invention includes also a method of producing refrigerationwhich comprises repeatedly perform ing the cycle of admitting compressedgas to a relatively long and narrow chamber through an inlet situated atone end thereof, with abstraction of heat from the gas before it entersthe chamber abstracting heat from the chamber near the end thereofremote from the inlet, and exhausting compressed gas from the chamberwith expansion thereof within the chamber and with return of abstractedheat to the gas after it leaves the chamber,

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whereby refrigeration is made available at the end of the chamberadjacent the inlet.

The invention includes further a unit for use in refrigerationapparatus, comprising a tube open at one end and closed at the otherend, heat exchange means secured to the tube in thermal contacttherewith adjacent its closed end, a housing with an opening at each endsecured to the tube in communication with the open end of the tube andheatabsorbing packing within the housing for abstracting heat from gasentering the tube and for delivering heat to gas leaving the tube.

The invention will now be described, by way of example, with referenceto the accompanying drawings in which:

FIGURE 1 is a diagrammatic view of a single stage refrigerationapparatus according to the invention;

FIGURE 2 is a longitudinal section through a part of the apparatus shownin FIGURE 1;

FIGURE 3 is a longitudinal section through part of a two-stagerefrigeration apparatus according to the invention;

FIGURE 4 is a cross-section on the line 1VIV of FIGURE 3; and

FIGURE 5 is a diagram of the valve timings adopted and pressure changesoccurring in a typical operation of the apparatus illustrated in FIGURES1 and 2 and in FIGURE 3.

FIGURE 6 is a schematic view of a three-stage refrigeration apparatus inaccordance with the invention.

Referring to FIGURE 1, the refrigeration apparatus includes an elongatedtube 10, which is closed at its end 11 and communicates at its other endwith a thermal regenerator 12. A first heat exchange means 13, throughwhich a coolant fluid may be circulated by connecting pipes 14, 15 issecured to the tube 10 near its closed end 11 in thermal contacttherewith. A second heat exchange means 16 is similarly secured to thepipe 10 adjacent the thermal regenerator 12 and is provided withconnecting pipes 17, 18 for circulating a fluid to be used as arefrigerant therethrough.

The elongated tube 10, thermal regenerator 12 and heat exchange means 13and 16 are encased within a thermal insulating box 19 which may bepacked with insulating material or be under high vacuum.

The thermal regenerator 12 communicates via pipe 20 with a pipe line 21communicating at one end with the outlet 22 and at its other end withthe inlet 23 of a gas compressor 24. An after-cooler 25 is provided onthe outlet side of compressor 24 to remove heat of compression from gascompressed 'by the compressor.

An inlet valve 26 arranged to be operated *by a solenoid 27 to move fromthe fully open to the fully closed position and vice versa is set in gasline 21 and between compressor outlet 22 and tube 10, While an outletvalve 28 also arranged to be operated by a solenoid 2? to move from thefully open to the fully closed position and vice versa is set in gasline 21 and between tube 10 and compressor inlet 23. A gas reservoir 31is included in line 21 between compressor outlet 22 and inlet valve 26,while a further gas reservoir 32 is included in line 21 between outletvalve 28 and compressor inlet 23, these reservoirs serving in use asbuffers to eliminate fluctuation in pressure of gas admitted to tube 10through inlet valve 26 or exhausted from tube 10 through outlet valve28.

The structure of tube 10 is shown in greater detail in FIGURE 2, inwhich the reference numerals used in FIGURE 1 are used for the sameparts. Tube 10, which is made of stainless steel, is of circular crosssection having an internal diameter of and a Wall thickness of A and isabout 2'6" long, being closed at its end 11, as previously stated, andopen at the other end 33,

at which it is welded to one end of the regenerator 12 comprising astainless steel cylinder 34 of about 1" diameter and 2" long, packedwith 400500 discs 35 of 200 mesh stainless steel gauze. Each disc 35extends transversely of cylinder 34, and the total weight of the discsis about 45 grams. An apertured cover plate 36 extends across the end ofcylinder 34 so as to prevent the discs from moving into the interior oftube While allowing gas to flow thereto.

To the end of cylinder 34 remote from tube 10, is welded a short lengthof stainless steel pipe 20 which passes through the wall of insulatingbox 19 and communicates with gas line 21 between inlet valve 26 andoutlet valve 28. Pipe 20 communicates with the interior of cylinder 34through a cover plate 37 which is apertured similarly to cover :plate 36so as to prevent the discs from moving into pipe 20 while allowing gasto flow between the pipe and the cylinder.

The heat exchange means 13 comprises a length of stainless steel tubingabout 10" long which is silver soldered to the tube 10 along the portionthereof which extends inwardly from closed end 11, and is connected bysupply and return lines 14 and 15 to a source of cooling water disposedoutside cold box 19. Similarly heat exchange means 16 comprises a lengthof stainless steel tubing about 6" long which is silver soldered to tube10 along the portion thereof which is near open end 33 and is connectedto supply and return lines 17 and 18 for circulating a cold-transferringfluid refrigerant therethrough. When the apparatus is in operation,tubing 13 constitutes a heat-sink while tubing 16 c0nstitutes acold-sink.

In using this apparatus for producing refrigeration, a suitable workinggas is argon which has a high ratio between its specific heat atconstant pressure and specific heat at constant volume, and an exampleof operation of this apparatus using argon will now be described.

The compressor 24 delivers argon at room temperature and a pressure of220 pounds per square inch gauge to reservoir 31 whence argon is takenat substantially 220 p.s.i.g. according as valves 26 and 28 are openedand closed in a repeated cycle determined by the operation of thesolenoids 27 and 29. In one particular cycle inlet valve 26 is openedand allowed to remain open for 0.24 second while outlet valve 28 remainsclosed. Consequently a charge of argon flows through pipe andregenerator 12 into tube 10 until a pressure of substantially 220p.s.i.g. is attained therein near closed end 11. The compression ofargon which is in the tube at the commencement of the cycle raises thetemperature of this argon and heat is transferred to the walls of theend portion of the tube 10, whence it is removed by cooling water intubing 13 at a temperature of about 290 K.

After approximately 0.045 second from the closure of inlet valve 26,outlet valve 28 is opened and remains open for 0.24 second, while inletvalve 26 remains closed. Argon thereupon flows from tube 10 throughregenerator 12 and pipe 20 to reservoir 32 and thence to the compressorinlet 23 at a pressure of almost 0 p.s.i.g. In flowing out of the tube,the compressed argon is expanded and, having lost heat to the coolingwater, is thereby cooled to a temperature below room temperature. Thewall of tube 10 near open end 33 is therefore cooled, and theregenerator discs 35 are also cooled.

After approximately 0.045 second from the closure of outlet valve 28,inlet valve 26 opens again and the cycle is repeated, a complete cycletherefore taking 0.57 second. Argon entering tube 10 when the cycle isrepeated is initially cooled in passing through the regenerator 12 butcompression of the gas in tube 10 causes heating .at its end 11. Heat isremoved by heat sink 13 before the gas is cooled on expansion giving upcold to the cold sink 16 and being warmed to room temperature on passingthrough the regenerator 12.

After approximately minutes of operation, the regenerator 12 has beencooled to a temperature of about K. at the end thereof adjacent tube 10,while at its end communicating with pipe 20 the temperature of theregenerator is about 290 K., .a rectilinear temperature gradientextending through the regenerator. These are equilibrium temperatures atwhich the regenerator is not further cooled by continued operation ofthe apparatus, and when equilibrium is reached, continued operation ofthe apparatus makes cold available to the cold sink.

Operating the apparatus as described, so that argon is taken fromreservoir 31 at the rate of about 2.9 cubic feet per minute, the argoncompressed at the end 11 of tube 10 attains a mean temperature of 350 K.after equilibrium is reached, while the wall of the tube near that endis maintained at about 290 K. Some improvement in heat transfer from thetube may be effected by making its warm end of a material moreconductive than stainless steel, but stainless steel offers theadvantage that there is no excessive conduction along the tube and theheat transfer is adequate. Near the cold end of tube 10, the wall of thetube is maintained at a temperature of 150 K., and refrigeration isdelivered at this temperature at the rate of about 1 Watt to acold-transferring liquid or gas which is continuously circulated betweencold sink 34 and the point at which refrigeration is required.

While specific data adopted or measured in a working model of theapparatus have been described in the above example, it will beappreciated that these figures are not critical, though indicative ofranges within which operating conditions preferably lie. For example,the dimensions of the tube may advantageously vary so as to give across-sectional area between one sixteenth and one half of a squareinch, and a length between eighteen inches and six feet. In a relativelyshort tube, the cross-sectional area may be up to four square inches.Gases other than argon may be used, and in particular air may be used,being taken from an available source of compressed air and beingexhausted from the tube to atmosphere.

Gas pressures used preferably lie in the range 150 to 300 p.s.i.g. Thevalves are suitably timed so that the apparatus operates between 200cycles and 5 cycles a minute, a preferred rate being between 150 and 60cycles a minute, the inlet valve preferably being open for the samelength of time as the outlet valve while the interval between theclosure of one valve and the opening of the other is preferably not morethan 0.05 second.

It will be apparent that if heat is withdrawn from the warm end of thetube at a temperature substantially below room temperature, the cold endof the tube will be cooled to a temperature well below the 150 K.described. Cooling of the warm end to a temperature below roomtemperature can be achieved by coupling two or more tubes operating in asimilar fashion to tube 10 so that the cold end of one cools the warmend of the next succeeding tube. Refrigeration apparatus in which twotubes are coupled in a particularly advantageous way for this purpose isillustrated in FIGURES 3 and 4.

One of the tubes illustrated in FIGURE 3 is generally similar to thatshown in FIGURE 2, so like parts have been accorded like referencenumerals and will not be further described. Tube 10 is spaced fromregenerator cylinder 34 by a distance a little over one foot, and theopen end 33 of the tube is connected to cylinder 34 of regenerator 12 bya copper tube 38 of A2" internal di ameter. Copper tube 38 communicateswith an annular channel 39 formed in a cover plate 40 of cylinder 34,channel 39 in turn communicating with the interior of the cylinder 34through holes 41. The central portion 42 of cover plate 40 is formedwith holes 4-3 through which gas can pass from regenerator 12 to afurther regenerator 44. Regenerator 44 comprises a cylinder 45 of about/2 internal diameter and 1" long, and is made of stainless steel, beingpacked similarly to cylinder 34 with 200 mesh stainless steel gauzediscs 46. Cylinder 45 communicates at its end remote from cylinder 34with the open end 47 of a stainless steel tube 48 of internal diameterand about 1'6 long which extends parallel to tube 38 and overlaps tube10. Tube 48 has a closed end 49, and the end portion of tube 48 adjacentend 49 is silver-soldered to the overlapped end portion of tube A coldsink 50 about 4" long and similar to cold sink 16 shown in FIGURE 2 issilver-soldered to tube 48 near its open end 47 and has supply andreturn pipes 51 and 52.

The arrangement shown in FIGURE 3 is provided with a compressor 24,valves 26 and 28 and reservoirs 31 and 32 fitted to the pipe line 21 asshown in FIGURE 1.

In use of this two-stage apparatus, the valves 26 and 28 are opened andclosed to admit argon at a pressure of 200 p.s.i.g. and exhaust argon toa pressure of 0 p.s.i.g. while the warm end-portion of tube 10 is cooledby cooling water, exactly as described for the preceding example. Theportion of tube 10 adjacent open end 3-3 is thereby cooled, thus coolingthe warm end portion of tube 48. Thus, in tube 10 a first stage ofrefrigeration occurs, while in tube 48 a second stage of refrigerationoccurs. In this second example, the cold-end portion of tube 48 and theadjacent regenerator packing discs 46 are in consequence cooled to atemperature of about 120 K., and when equilibrium is reachedrefrigeration is available at this temperature at the rate of 1.5 watts.

The valve timings and consequent changes of gas pressure within thetubes for the two stage apparatus are illustrated in FIGURES 5a and 50respectively. It will be apparent that the valve timings are the same asfor the single stage operation, the pressure changes for which are shownin FIGURE 5b.

More than two tubes can be coupled together to produce still lowertemperatures, down to K.

A suitable arrangement of a three-stage unit is schematicallyillustrated in FIGURE 6, in which 51 represents the compressor (within-built after-cooler), 52 and 53 the two reservoirs, 54 and 55 theinlet and outlet valves respectively, 56 the gas pipe line, 57, 5'8 and5-9 the three elongated tubular members with thermal regenerators 60, 61and 62 respectively. Heat is abstracted from the closed ends of tubularmembers 57, 58 and 5-9 by indirect heat exchange at points 63, 64 and 65respectively and refrigeration is supplied at end 66 of tubular member59. 6 7 is the thermal insulating or cold box.

The fluid circulated through tubing 16 may be any suitable gas or liquidwhich does not freeze at the low temperatures attained. Nitrogen,hydrogen, argon, helium or air may, for example, be used whereappropriate. An organic liquid such as acetone may be used undersuitable conditions of temperature.

Instead of supplying cold to a fluid as shown at cold sink 16 in FIGURES1 and 2, an article to be cooled to, and maintained at, a lowtemperature may be soldered or clamped to the tube 10 in place of thetubing 16.

By a thermal regenerator is meant any means which is adapted insuccessive operations to abstract heat from, and to give up heat to, agas passing therethrough.

The heat exchange means which may be used for the circulation of a fiuidin thermal contact with the tubular member 10 may be arranged externallyof the tube 10 in physical contact therewith or may be within the tubewith connections leading to the outside of the tube.

I claim:

1. Refrigeration apparatus comprising a tubular memher which is open atone end and closed at the other end, a thermal regenerator incommunication with the open end of the tubular member, a gas conduit incommunication with the thermal regenerator so that gas under pressuremay be passed from the gas conduit through the thermal regenerator tothe tubular member and exhausted with expansion from the tubular memberthrough the thermal regenerator to the gas conduit, the thermalregenerator serving to abstract heat from gas entering the tubularmember and return heat to gas leaving the tubular member, valve means insaid gas conduit for controlling the flow of gas to and from the tubularmember and arranged to permit the gas to enter and leave the tubularmember as a succession of charges and heat exchange means adjacent theclosed end of the tubular member for enabling a coolant to be passed inthermal contact with the tubular member adjacent to the closed endthereof, whereby on operation of the apparatus with gas under pressurebeing fed into, and exhausted with expansion from, the tubular member asa succession of charges and with a coolant passing through the said heatexchange means refrigeration is made available near the open end of thetubular member adjacent the thermal regenerator.

2. Refrigeration apparatus as claimed in claim 1, in which the tubularmember is a tube of internal crosssectional area of from one sixteenthto one half of a square inch, and of a length of from eighteen inches tosix feet.

3. Refrigeration apparatus as claimed in claim 2, in which the tubularmember is made of stainless steel and has a wall-thickness between 0.02inch and 0.1 inch.

4. Multi-stage refrigeration apparatus as claimed in claim 18, in whichthe valve means include a single inlet valve and a single outlet valvecommon to all the tubular members and the passage means is arranged toadmit gas in parallel to the tubular members.

5. Multi-stage refrigeration apparatus as claimed in claim 4 includingfirst and second tubular members, and having a first thermal regeneratorarranged to cool gas being admitted to the first and second tubularmembers, and a second thermal regenerator arranged to further cool gasbeing admitted to the second tubular member.

6. Multi-stage refrigeration apparatus as claimed in claim 5, in whichthe open end of the first tubular member is spaced from the firstthermal regenerator by a relatively narrow tubular gas passage, and thesecond tubular member extends parallel to and adjacent the tubular gaspassage, a portion of the second member near its closed end overlappinga portion of the first member near its open end and adjacent portions ofthe first and second members being in thermal contact so that the firstmember provides refrigeration for the second member.

7. A unit for use in refrigeration apparatus, comprising a tube open atone end and closed at the other end, heat exchange means secured to thetube in thermal contact therewith adjacent its closed end, a housingwith an opening at each end secured to the tube in communication withthe open end of the tube and heat-absorbing packing within the housingfor abstracting heat from gas entering the tube and for delivering heatto gas leaving the tube.

8. A method of producing refrigeration which comprises repeatedlyperforming the cycle of admitting compressed gas to a relatively longand narrow chamber through an inlet situated at one end thereof, withabstraction of heat from the gas before it enters the chamber, coolinggas in the chamber by indirect heat exchange near the end thereof remotefrom the inlet, and exhausting compressed gas from the chamber throughthe inlet with expansion thereof within the chamber and with return ofabstracted heat to the gas after it leaves the chamber, wherebyrefrigeration is made available at the end of the chamber adjacent theinlet.

9. Refrigeration apparatus comprising 'a tubular member which is open atone end and closed at the other end, a thermal regenerator incommunication with the open end of the tubular member, a gas conduit incommunication with the thermal regenerator so that gas under pressuremay be passed from the gas conduit through the thermal regenerator tothe tubular member and exhausted with expansion from the tubular memberthrough the thermal regenerator to the gas conduit, the thermalregenerator serving to abstract heat from gas entering the tubularmember and return heat to gas leaving the tubular member, valve means insaid gas conduit for controlling the flow of gas to and from the tubularmember and arranged to permit the gas to enter and leave the tubularmember as a succession of charges, heat exchange means adjacent theclosed end of the tubular member for enabling a coolant to be passed inthermal contact with the tubular member adjacent to the closed endthereof whereby on operation of the apparatus with gas under pressurebeing fed into, and exhausted with expansion from, the tubular member asa succession of charges and with a coolant passing through the said heatexchange means refrigeration is made available near the open end of thetubular member adjacent the thermal regenerator, and a second heatexchange means which is in thermal contact with the tubular memberadjacent the open end thereof, and through which a fluid may becirculated.

10. Refrigeration apparatus as claimed in claim 9 in which the thermalregenerator comprises a housing with an opening at each end and packedwith discs of metal gauze, each disc extending transversely of thedirection of gas flow through the housing.

11. Refrigerator apparatus as claimed in claim 9 in which the said heatexchange means for the passage of coolant includes at least one tubewhich extends parallel to the tubular member and in thermal contacttherewith adjacent the closed end thereof.

12. A method of producing refrigeration which comprises repeatedlyperforming the cycle of admitting compressed gas to a relatively longand narrow chamber through an inlet situated at one end thereof, withabstraction of heat from the gas before it enters the chamber, coolinggas in the chamber by indirect heat exchange near the end thereof remotefrom the inlet, and exhausting compressed gas from the chamber throughthe inlet With expansion thereof Within the chamber and With return ofabstracted heat to the gas after it leaves the chamber, said admittingand exhausting of compressed gas being for substantially equal periodsof time, whereby refrigeration is made available at the end of thechamber adjacent the inlet.

13. A method as claimed in claim 12, in which the cycle is performedbetween 200 times and times a minute.

14. A method as claimed in claim 12 in which the cycle is performedbetween 150 times and 60 times a minute.

15. A method 'as claimed in claim 12 in which the gas is admitted to thechamber at a pressure between 150 and 300 pounds per square inch.

16. A method as claimed in claim 12 in which the gas is argon.

17. A method as claimed in claim 12 in which compressed gas issimultaneously admitted to and exhausted from a plurality of chambers,and refrigeration made available at the wall of one chamber is used tocool the Wall of another chamber near the end thereof remote from theinlet so that lower temperature refrigeration is made available at thewall of said another chamber adjacent the inlet thereof.

18. Multi -stage refrigeration apparatus comprising at least twoelongated tubular members each open at one end and closed 'at the otherend, gas passage means in communication with the open end of eachtubular member through a thermal regenerator whereby gas under pressuremay be passed from the gas passage means through the thermal regeneratorinto each tubular member and exhausted with expansion from the tubularmember back through the thermal regenerator and through the gas passagemeans, the thermal regenerator in each case serving to extract heat fromthe gas entering the tubular member and returning heat to the gasleaving the tubular member, valve means for controlling the admission ofgas to, and exhaustion of gas from, the tubular members, the valve meansbeing arranged to permit the gas to enter and leave the tubular membersas a succession of charges, and means for the passage of coolant inthermal contact with a first tubular member adjacent the closed endthereof, the part of each succeeding tubular member adjacent its closedend being thermally linked to the part adjacent the open end of thepreceding member for indirect heat exchange therewith, whereby asuccession of admissions of gas under pressure to the tubular memberswith exhaustion and expansion after each admission and with passage ofcoolant through the means in contact with the said first tubular memberadjacent its closed end during such operation, refrigeration is madeavailable for use adjacent the open end of the last tubular member.

References Cited by the Examiner UNITED STATES PATENTS 1,321,343 11/1919Vuilleumier 6288 1,459,270 6/1923 Vuilleumier 62-88 3,237,421 3/1966Gifford 62-88 WILLIAM J. WYE, Primary Examiner.

8. A METHOD OF PRODUCING REFRIGERATION WHICH COMPRISES REPEATEDLYPERFORMING THE CYCLE OF ADMITTING COMPRESSED GAS TO A RELATIVELY LONGAND NARROW CHAMBER THROUGH AN INLET SITUATED AT ONE END THEREOF, WITHABSTRACTION OF HEAT FROM THE GAS BEFORE IT ENTERS THE CHAMBER COOLINGGAS IN THE CHAMBER BY INDIRECT HEAT EXCHANGE NEAR THE END THEREOF REMOTEFROM THE INLET, AND EXHAUSTING COMPRESSED GAS FROM THE CHAMBER THROUGHTHE INLET WITH EXPANSION THEREOF WITHIN THE CHAMBER AND WITH RETURN OFABSTRACTED HEAT TO THE GAS AFTER IT LEAVES THE CHAMBER, WHEREBYREFRIGERATION IS MADE AVAILABLE AT THE END OF THE CHAMBER ADJACENT THEINLET.